How Does Exercise Heal Injured Tissues?

Each day we meet with athletes, clients, and patients who present with an injury or condition involving an injury to a muscle, nerve, ligament, tendon, or bone. One of the most powerful tools we have to accelerate the healing of this injury is exercise. A previous post discussed the impact of Physical Therapy exercises on Achilles Tendinopathy. This post described the impact on exercise on achilles tendinopathy and how exercise improves injured tissue a process called mechanotransduction. Mechanotransduction refers to the process by which the body converts mechanical loading into cellular responses (Khan Br J Sp Med 2015).

Khan et al. in a recent article used the term "mechanotherapy" to describe the benefits of Physical Therapy exercises on injured tissues in the body (Br J Sp Med. 2015). These authors updated the definition of this term to include "the employment of mechanotransduction for the stimulation of tissue repair and remodeling". Each day we utilize exercise parameters including direction of force, speed, intensity, frequency, duration, and others to optimally impact a patient's injured tissue in order to promote healing and restoration of function. Each tissue in the body seems to have unique responses to loading from Physical Therapy exercise.

A common example of this phenomenon occurs in our bones. Gradual loading of the bones through exercise improves bone density, but aging and a lack of weight bearing exercise can lead to osteoporosis. Bone cells (osteocytes) are stimulated through loading in weight bearing and exercise to promote fracture healing in injured bones. Research by Challis et al. examined the impact on loading in addition to standard fracture care in patients with forearm fractures (Aust J Phys 2007, J Bone Joint Surg Br 2006, Clin Orthop Relat Res. 2005). The authors noted improved fracture healing, strength, and range of motion when fractures were exposed to low load, cyclical pressures from a pneumatic cuff wore under the cast. This suggest gentle, controlled loading in addition to immobilization may accelerate fracture healing.

Muscle and tendon offer us some of the best examples of exercise's impact on tissue. The benefits of exercise on muscle are clearly known including increased size (hypertrophy) due to loading (weight training) and the loss of muscle size due to disuse or immobilization (cast). After a brief period of controlled rest after a muscular injury (strain) exercise has been shown to positively effect the cellular healing and repair of these injured tissues (Jarvinen et al. Best Pract Res Clin Rheumatol. 2007). Without proper loading these injured muscles may remain in a weakened state making them more prone to subsequent injury. We often see this in recurrent injuries such as hamstring strains.

Ohberg et al. examined the impact of achilles tendon exercises on achilles tendinopathy. These patients demonstrated quick improvements in pain and function, but they were also followed over the coming years to determine how their tendons healed from this exercise (Br J Sp Med 2004). The authors noted improved tendon structure with 19/26 tendons returning to "normal" quality on ultrasound imaging. As described in our previous blog post early pain relief and restoration of function is likely due to a different mechanism than tendon restructuring since these changes often take years to develop.

In short, Physical Therapy exercise will always be a hallmark conservative treatment for the regeneration of injured tissues. Utilize a Physical Therapist to learn how to best manage your injury and how to utilize specific exercise parameters in get back to life and sports.